Backpack



FIG. 1 is a front elevational view of the backpack according to my novel design;

FIG. 2 is a left-front perspective view of the backpack according to my novel design;

FIG. 3 is a top plan view of the backpack according to my novel design;

FIG. 4 is a bottom plan of the backpack according to my novel design; and,

FIG. 5 is a right side elevational view of the backpack according to my novel design.

The backpack straps and zipper grabbers are illustrated in broken lines for illustrative purposes only and do not form any part of the claimed design. 

The ornamental design for a backpack, as shown and described. 